The invention in a first aspect relates to mixer taps, also referred to herein as faucets, having separate controls for hot and cold water. The invention in a second aspect relates to thermostatic mixing valve, usable to provide thermostatic regulation of temperature integrated within the tap body or in a separate unit. The two aspects can be combined or used separately.
Mixer taps of various types are known, both for domestic use and for use in institutions such as hospitals, care homes and the like, where safety and ease of maintenance become important. A mixer tap generally comprises hot and cold inlets and a common outlet (spout, nozzle, shower head) for delivering a desired mixture of cold and hot water. Different forms of control are available to regulate the flow and the mix. Separate hot and cold regulating controls are simplest to provide, but can be difficult to adjust before the correct temperature and flow rate is reached. Each control may be a rotary knob or a lever, for example, and may move through a quarter turn or several turns, according to the type of head works. Single-lever mixer tap controls are another option. In one type, similar to a joystick, movement about a first axis regulates the flow and movement about a second axis controls the mix. Another form of control having a single lever is the so-called sequential control in which movement of a single lever about a single axis first enables the flow and then progressively alters the mix (usually starting from cold and progressing toward hot). Yet another form of control popular with thermostatic mixing taps is one in which a first control regulates the flow and a second control regulates the temperature via a thermostatic mixing valve.
For intuitive operation by persons unfamiliar with a particular installation, the applicant believes the simple dual control with one control on the hot water supply and a separate control on the cold water supply is to be preferred. Moreover, the simple dual control permits the user to be sure that a “cold” output contains water purely from the cold supply. Such an assurance is generally required before water can be used for drinking (“potable water”), or even brushing teeth, for example. With the other types of mixer control, there is no certainty that a small proportion of water from the hot supply is not included in the output. This might arise either from failure to set the control lever fully to the cold position, from poor design or from wear and tear of the valve components or from a deterioration in the performance of the thermostat element, due to wear and tear, in a thermostatic tap. In either case, a separate tap for drinking water must be provided, and inconvenience for the user, together with increased installation costs.
In safety-sensitive installations, the “hot” water output is typically a mix of hot water from the domestic hot water services (DHWS) at a temperature which is typically above 50° Celsius and cold water at ambient temperature, provided by a thermostatic mixer to ensure that water above, say, 40 or 42 degrees Celsius cannot be emitted even at the hottest setting. If a variable temperature thermostat is part of the mixing tap, as in a shower installation, then the thermostatic valve is naturally included in the tap body. Where a simple hot/cold mixer tap is required, for example over a basin for washing hands or dishes, the usual solution is to provide a thermostatic mixing valve separately from the tap fitting, for example beneath the sink or behind a wall panel. The same thermostat might provide a supply of such “mixed hot” water for more than one basin, using the DHWS hot and cold water service (CWS) supplies of the building, but only for a few and only in one location.
Thermostatic and other valves require regular maintenance to continue safe operation, and require strainers at their inlets to guard against ingress of particles to the intricate mechanism. All these different parts make the plumbing installation complex and costly to install. Regular maintenance is hampered by the awkward location of the valves under basins and behind panels, and frequently does not take place as it should. To simplify these installations, there have recently been brought to market some mixer taps for institutional applications in which the thermostat for providing a supply of “safe” (mixed) hot water is incorporated within the body of the tap itself. The temperature of mixing may or may not be variable, depending on the design. These new taps still leave a lot to be desired, however, when it comes to ease of maintenance of the thermostat, strainers and the like. The body of the integrated tap may need to be dismantled in several steps and even removed entirely from the wall in some cases, before access is obtained to the thermostat or other parts. Given the bulk of brass (typically) involved in accommodating the mechanism, these bodies may weigh 6 kg or more, and are not trivial to handle safely. Even where the TMV is mounted separately from the tap, servicing can be difficult.
The invention in its various aspects aims to enable the provision of safe hot water while avoiding or reducing one or more of the problems identified above.